Start with the cake. Sift together the flour, dark cocoa powder, baking powder and salt in a large bowl. Set aside. In a medium bowl, combine the sour cream and vanilla and almond extracts. Set your wet ingredients bowl aside, as well.

Cream the butter and sugar in the bowl of a standing mixer fitted with a paddle attachment. Keep the mixer on medium speed until smooth, then set it on low speed as you add the eggs, one at a time, until combined. Starting and ending with the flour mixture, add the dry ingredients and wet ingredients mixtures in an alternating fashion. Scrape the sides of the bowl between additions and ensure each is properly combined before switching bowls. With the mixer still on low, slowly add the room temperature coffee into the batter and beat until combined. (Note that standard will also do, and is what the Confetti Cakes recipe calls for, but I highly recommend you use French Vanilla flavored.)
Preheat your oven to 350ºF. Divide the batter evenly into liner lined cupcake pans, filling each cup to about ½ full. (This is important! This recipe tends to rise more than others, and to avoid it overflowing, you want to use less batter. The Confetti Cupcakes recipe doesn’t explicitly tell you how much to put in, but in order to get the 24 cupcake yield they estimate, it would need to use a lot more than you really should be putting in.) Bake for 20 to 25 minutes, or until a toothpick comes out barely clean so as not to overbake, then set aside to cool.
While the cupcakes are cooling, start the ganache. In a saucepan over medium heat, warm the heavy cream. Slowly add in the Nutella, small measured spoonfuls at a time, and stir in between additions until it is combined. When all of the Nutella has been added, set the saucepan aside to cool and thicken slightly.

Using a butter knife, cut a circle in the cupcake that is about an inch wide and thins into a cone shape. Do not cut so deep that you cut clean through to the bottom. Remove the piece of cake and cut off the cone so the circle becomes a coin. Repeat this for all of the cupcakes. When the Nutella ganache has cooled, use a spoon to fill the hole with the ganache. Leave a little room so that you can replace the coin top and push it into the hole until it is level with the rest of the cupcake top while ensuring no filling overflows. If it does, lightly scrape it off so the surface of the cupcake is clean. Set the cupcakes aside.
Make the buttercream. In the bowl of your stand mixer, cream the butter and Nutella until combined. Add in the confectioner’s sugar in one cup increments, allowing each addition to combine before the next is put in. Continue creaming the mixture until it is all well blended.

Adjust your mixer to a low speed and add the salt and vanilla extract to the mixture. Add the heavy cream, one tablespoon at a time, until your buttercream consistency is right (for me, it took 8 tablespoons). Adjust your speed setting to high to fluff the frosting, then transfer to a piping bag or tool. Pipe onto the cupcakes as desired, and top with finely chopped hazelnuts. (Note that I bought pre-chopped hazelnuts and cut them down even further. You want the crunch of a Rocher without throwing off the overall texture of the cupcake.)